1. FIELD OF THE INVENTION
This invention relates to a packing line for packing stacks of rectangular tinplate sheets on pallets, and more particularly to such a packing line arranged at the end of a tinning line in which steel strip is continuously tinplated and then cut into rectangular sheets which are stacked and packed in the packing line.
2. DESCRIPTION OF THE PRIOR ART
The packing of tinplate sheet stacks at the end of a tinning line presents particular problems. Though not very bulky (typically 80 cm.times.80 cm.times.30 cm), the stacks are heavy (e.g. 2 tons). The packed stack must therefore be capable of being easily handled and moved by means of a fork lift truck. This means that pallets must be employed. Tinplate is rather easily damaged, as the individual sheets are thin and they have a high-quality surface finish, but the packed stack will inevitably be subjected to rather rough treatment in its life. The packing must endeavour to protect the sheets from the effects of rough treatment, in particular to protect them against moisture and to prevent, if possible, that the sheets slide relatively one over another if the stack is subjected to a shearing force.
Another problem is that conventionally a number of different packings are used, the durability of the packing increasing with the distance which the packed stack is to travel to its consumer. As a result, any packing line must be able to cope with a variety of different packings, which makes automation extremely difficult. A number of different packings are described below.
A packing line for steel sheets is described in U.K. patent specification No. 1,250,707. It has a plurality of conveyors, a packing station at which packing is performed manually and a strapping machine. An automatic strapping machine must work transversely of the conveyor path, but where a roller conveyor is used to move a pallet, the runners of the pallet must extend parallel to the conveyor path (i.e. transverse to the roller axes) which makes use of an automatic strapping machine impossible.
Conventionally then, the degree of automation of the tinplate sheet stack packing line is low. The job is time-consuming and labour-intensive, as many as six packers being simultaneously required. Furthermore, the environment, being adjacent the shearing machine which is cutting the plate strip, is noisy.